Calculate the mass fraction of nitrogen in nitric and nitrous acid.

HNO3- nitric acid
HNO2- nitrogenous acid
Let’s find the mass fraction of an element by the formula
w (element) = Ar (el-ta) / M (in-va), where w is the mass fraction of the element, Ar is the atomic mass of the element, M is the molar mass of the substance
M (HNO3) = 1 + 14 + 16 × 3 = 63 g / mol
M (HNO2) = 1 + 14 + 16 × 2 = 47 g / mol
w (N) = 14/63 = 22.22% – in nitric acid
w (N) = 14/47 = 29.78% – in nitrous acid